The present invention relates to technologies for processing images photographed by such devices as an in-vehicle camera.
In recent years, the development has been proceeding concerning the following technology: The external environment of a vehicle is recognized based on the images photographed by an imaging device mounted on the vehicle. Moreover, the automatic driving or driving assistance is performed based on the recognition result.
When detecting a target outside a vehicle by processing the images photographed by an imaging device, in some cases, the detection process cannot be appropriately performed due to influences exerted by such a cause as sunlight or other vehicle's headlight. As a solution for this problem, there has been known the following technology (refer to, e.g., JP-A-05-205196): One image input device is provided at each of the front and rear of the vehicle. Then, if contrast of an image photographed by the front-positioned image input device becomes lower, an image photographed by the rear-positioned image input device is selected. Moreover, based on this image information selected, the running route is recognized.
The causes for making the image recognition difficult are not limited to such a cause as sunlight or headlight. In some cases, depending on a cause concerned, the environment information is sufficiently obtainable without switching the image to be processed from the front view to the rear view. As a result, the image recognition is executable even in a situation where the image recognition was impossible conventionally. Also, in the irradiation with the sunlight or headlight, when no obstructing object exists in the surroundings, the irradiation continues in a time-interval which is longer than a certain constant one. However, when, in the evening, the vehicle is running between buildings, or when the headlight is directed at the vehicle by a vehicle coming from the opposite direction in such a place as an expressway having a central divider of hedge, a state where the vehicle is illuminated with the sunlight or headlight and a state where the vehicle is intercepted from the sunlight or headlight are repeated alternately in a short while. In a case like this, according to the above-described technology, it turns out that the image switching processing between the front view and the rear view is performed so frequently. As a result, there exists a possibility that the running environment cannot be satisfactorily recognized depending on a time needed for the image processing.
In view of the above-described problem, an object of the present invention is to provide an in-vehicle image recognition processing which exhibits a higher accuracy.